The present invention relates to a process for producing fluorosilicone polymers and more particularly the present invention relates to a process for producing triorganosilyl end-stopped diorganopolysiloxane fluids in high yield.
Fluorosilicone polymers are well-known. Fluorosilicone polymers, while not the most common of silicone polymers, are recognized in the art. The advantage of such fluorosilicone polymers is that they can resist certain solvents much more effectively than ordinary silicone polymers. These polymers have this effective resistance to hydrocarbon solvents due to the presence of a 3,3,3 trifluoropropyl group in the polymer chain. Accordingly, such polymers, while expensive to make, find ready use as electrical connectors and the like in places where the connector will come in contact with the solvent. Such fluorosilicone polymers, in the case of heat vulcanizable silicone rubber compositions, are produced by taking trifluoropropene and reacting it with a hydrogensilane so as to produce methyl 3,3,3-trifluoropropyldichlorodisilane. The dichlorosilane is then hydrolyzed in water and the hydrolysate is cracked in the presence of an alkali metal hydroxide and other indgredients to preferentially distill overhead a cyclotrisiloxane. The cyclotrisiloxane is then taken and then in the presence of minor amounts of alkali metal hydroxide catalysts or alkali metal catalysts of various kinds, the cyclo trisiloxane is polymerized very rapidly in almost 100 percent yield to a linear diorganopolysiloxane gum having a viscosity of anywhere from 500,000 to 300,000,000 centipoise at 25.degree. C., where the organo substituting groups in the polymer are methyl and 3,3,3 trifluoropropyl. Co-polymers may be produced to a certain extent by equilibration of dimethylcyclotrisiloxanes with the fluoropropyl cyclotrisiloxanes. It should be noted that recently there has been some work carried out by the General Electric Company in the polymerization of fluorosilicone substituted cyclotetrasiloxane. Such fluorosilicone cyclotetrasiloxanes are polymerized to some extent to form linear diorgranopolysiloxane gums of the desired viscosity but the yield is not as high as with the cyclotrisiloxane.
Accordingly, for the production of gums, the fluorosilicone substituted cyclotrisiloxanes are preferred. The gums may then be taken and there may be incorporated into them the desired amounts of filler treated or untreated; and process aids, preferably vinyl containing silicone process aids. Then there is added to the composition a peroxide catalyst such that it can cure to a silicone elastomer at elevated temperatures that is temperaures about 100.degree. C. Examples of fluorosilicone technology are to be found in the following U.S. Pat Nos. 2,979,519; 3,179,619; 3,006,878; 3,002,951; 3,630,982; 3,377,284; 2,961,425; and 3,386,945.
It is found that when such gums were produced that the chain-stoppers did not participate sufficiently in the polymerization. Alternatively, in the production of dimethyl polysiloxane gums that is polymer having a viscosity from 500,000 to 300,000,000 centipoise at 25.degree. C., the presence of trimethylsiloxane end-stopped low molecular weight polymers as chain-stoppers controls and final molecular weight of the composition. However, with respect to fluorosilicone polymers when it is attempted to form a gum, the polymer will rapidly polymerize to a high molecular weight polymer. However, with the use of chain-stoppers in such reaction, it was found that the traditional chain-stoppers would react into the composition only very slowly. Accordingly, if it was desired to obtain gums with triogranosiloxy end-stopped groups, the chain-stoppers would react so slowly into the gum that the gum would degrade to form cyclics such that after a period of time passed for all of the chain-stoppers to react into the gum there would result a relatively low yield gum with the siloxy end-stopped units since the rest of gum would have reverted to cyclic material. Accordingly, it was desired to produce or have an effective chain-stopper for the production of fluorosilicone substituted diorganopolysiloxane gums in which the chain-stopper will react rapidly into the gum that was formed. Accordingly, as a result of this problem, there evolved the use or the development of the use of silanol-end stopped siloxane as a chainstopper in the production of fluorosilicone polysiloxane gums. This work is disclosed in a patent application of Ben A. Bluestein et al filed Nov. 13, 1978, entitled "Process for Producing Fluorosilicone Polymers", Ser. No. 959,544. The above docket also indicates that high molecular weight alcohols can also be utilized as chain-stoppers in a production of fluoropropyl polysiloxane gums. It was found that such silanol end-stopped fluoropropyl substituted polysiloxane gums would function effectively to produce a fluorosilicone substituted heat curable composition which can cure to a silicone elastomer which silicone elastomer had desired solvent resistant properties.
Proceeding to a slightly different branch of fluorosilicone chemistry, it was indicated by the prior art that also by similiar methods as the above dimethyl polysiloxane fluids are formed (by fluids it is meant a linear diorganopolysiloxane polymer having a viscosity of 50 to 50,000 centipoise at 25.degree. C.) and that such fluids could be formed by the reaction of cyclotri or tetra siloxanes with low molecular weight triorganopolysiloxane chain-stoppers in the presence of strong acid catalyst. Accordingly, in dimethyl silicone polymer chemistry it is well known to react cyclotetrasiloxanes with low molecular weight triorgansiloxy end-stopped chain-stoppers such as disiloxanes for instance, hexamethyldisiloxane in the presence of toluene sulfonic acid or acid treated clay to produce the desired fluid. It should be noted here that such fluids are desired for instance to produce silicone greases, silicone hydraulic fluids, silicone anti-foam compositions, silicone paper release compositions, etc. Accordingly, the prior art indicated that when it was desired to produce a fluorosilicone fluid that such a fluorosilicone fluid could be produced by the equilibration or reaction of fluorosilicone cyclotrisiloxane in the presence of acids to form the desired fluid in much the same way that the dimethyl fluids were formed, the only difference being there was utilized a cyclotrisiloxane instead of a cyclotetrasiloxane. Examples of such art which was related to the production of fluorosilicone fluids which were polymers and copolymers are to be found in Brown et al, U.S. Pat. No. 3,607,899, U.K. Pat. No. 899,659 Pending Group 170. Pierce et al U.S. Pat. No. 2,961,425, Currie et al German Pat. No. 1,189,170, U.K. Pat. No. 899,661, and the Publication C. Eaborn, "Organosilicon Compounds," published by London, Butterworths and Company. The only difficulty with such equilibration reactions as those indicated in the foregoing publications and patents is that the hexamethyldisiloxane and other low molecular weight triorgano siloxy chain-stoppers would equilibirate into the fluid that was formed only slowly. As a result, there would be formed a large amount of cyclics, since most of the cyclopolysiloxanes react immediately or in less than a half hour to form the linear polymer and then some of it degrades to form cyclics. Accordingly, it was difficult to obtain a yield of ninety percent or more of the desired fluid utilizing this procedure; such yield being determined on the basis of the initial cyclotrisiloxane. Accordingly, it was highly desireable to find the means for increasing the yield of fluorosilicone polymer and copolymer fluids produced from a fluorosilicone cyclotrisiloxane.
Accordingly, it is one object of the present invention to provide for a process for producing high yields of fluorosilicone substituted fluids from fluoro substituted cyclotrisiloxanes.
It is another object of the present invention to provide a process or method for producing high yields of fluorosilicone polymers and copolymers from fluorosilicone substituted cyclotrisiloxanes.
It is yet an additional object of the present invention to have an efficient and economical process for producing fluorosilicone polymer fluids and copolymer fluids from fluorosilicone substituted cyclotrisiloxanes. These and other objects of the present invention are accomplished by means of the disclosure as set forth herein below.